Various types of methods and apparatuses have been known in the art to mix, for example, water with carbon dioxide gas and to impregnate water with the gas, (cf., for example, DE-AS 11 92 598, U.S. Pat. No. 2,241,018 or United Kingdom patent specification 13 71 466). Furthermore, it is known to mix gas and water in a mixing nozzle (cf. United Kingdom patent specification 12 74 363).
All methods known in the art have the disadvantage that the degree of impregnation is relatively low, that the gas passes through the water in the form of relatively large bubbles (nevertheless these bubbles are understood to be very small, however, still relatively large when an optimum fine impregnation is intended to be achieved) or that the effort of impregnation by cooling or very high pressures, for example, is relatively great.
Relatively large bubbles present in the impregnated liquid easily result in a separation of gas and water, obstruct the reliable function of dosing devices or clog capillaries in drip irrigation systems or the like. If the degree of impregnation is not sufficiently high, a relatively large quantity of gas is released from the liquid owing to a decrease of pressure at the liquid outlets.
It is known that the health of plants, their growth and their resistance to infestation can substantially be improved when the plants are watered with a liquid containing a large amount of carbon dioxide (CO.sub.2) and a correspondingly large amount of carbonic acid (H.sub.2 CO.sub.3), with the essential point that the arable land itself is watered with a liquid containing a large amount of these substances. For this purpose, adequate devices have been developed for horticultural businesses, outdoor cultivations and re-afforesting areas (cf. German journal "Der Spiegel". No. 47/1982, pages 99 to 101).
Furthermore, watering and fertilizing systems are known for household purposes and hobby gardeners with the aid of which plants or patches of plants can be supplied to the extent required with irrigation water and fertilizers for a longer period of time.